The Big Idea Design Mini Click Pen - Black Titanium is super compact and great for quick notes and signatures throughout your day. Never in the way, simply there when you need it. This pen accepts many different D1 Style Refills that are to find and swap out. Yes, it also work with the ever popular Hi Tec-C Slims and the Fisher Space Pen "UF" Pressurized series refills also fit if you ever need to write in space or upside down in a river.